[sdiy] tube phono (a little OT)

[Gavin Russom]

Thanks for all the replies on this query,  I guess I'm going to take the
project on, hopefully learn something!  I'll post an update when I start
getting some results!
----------
>From: "Jay Schwichtenberg" <jays at aracnet.com>
>To: "Gavin Russom" <elmystico at earthlink.net>
>Subject: RE: [sdiy] tube phono (a little OT)
>Date: Sun, Feb 10, 2002, 7:22 PM
>

>Gavin,
>
>Several ideas:
>
>* One of the first things that deteriorate over time is caps. Check or
>replace all of them, not just the electrolytics. Good chance that the PS
>caps aren't working, especially since it hums independent of the volume
>control.
>
>* Next check the rectifier. This maybe either a tube or solid state. Be
>careful of solid state retifier replacements. Two problems with them. First
>is that they turn on immediately when a tube starts up slow. This can shock
>the tubes and cause failures. Also they do not have the same voltage drop
>that a tube has and usally put out more voltage. So you might have to put
>more series resistance in the filter circuit to drop the voltage some.
>
>* Check all the tubes. Some high end hi fi shops still have and use tube
>testers.
>
>* Check all the transformers and look at their leads and cases. Make sure
>they don't look totally rusted or burnt up.
>
>Good luck.
>Jay
>
>> -----Original Message-----
>> From: owner-synth-diy at dropmix.xs4all.nl
>> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Gavin Russom
>> Sent: Sunday, February 10, 2002 12:36 PM
>> To: synth
>> Subject: [sdiy] tube phono (a little OT)
>>
>>
>> A friend and I are trying to repair an old tube phonograph with a built in
>> speaker.  It hums loud!  Sounds to me like a grounding problem... The hum
>> doesn't change volume when you turn the volume pot.  I do ok with analog
>> synth DIY and troubleshooting, repairs as well.  Any suggestions? Am I in
>> over my head with this one?
>>
>>
>
>